The invention provides a process for preparing oil and petrol-resistant cellular to solid (polyurea)polyurethanes (PURs) with improved physical properties, such as are required for personal safety equipment and for the construction of automobiles.
The wide variety of polyurethane plastics, their structure and methods of preparation has represented the prior art for many years. WO 98/23659 describes polyetherpolyurethanes which are relatively petrol-resistant. However, these swell in an obvious manner on contact with hydrocarbons and thus their mechanical and physical properties become modified. In addition, when processing polyetherpolyurethanes to produce moulded articles, the moulds become heavily soiled.
The polyester-PURs generally used hitherto in such applications have the following disadvantages:                the high viscosity of the components when ready for processing leads to problems with the accurate reproducibility of moulded articles;        the temperatures of 40–60° C. required for processing reduces the useful lifetime of the system components;        inadequate resistance to hydrolysis and microbes leads to a limited operational lifetime for the products;        the ability to control the polyaddition reaction by catalysts is restricted since these often promote glycolysis of the ester.        